Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 240830
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
330 AM CDT Tue Mar 24 2015

.SHORT TERM...(Today)
ISSUED AT 329 AM CDT TUE MAR 24 2015

A band of mid-level warm frontogenesis will advance into central IL
from the west this morning, causing rain showers to eventually
develop through the dry low level airmass. The leading edge of the
rain band will likely encounter areas with surface temps at or just
below freezing, but not sure how far south will freezing rain
affect. 08z obs show only Jacksonville and Lawrenceville above
freezing, while the remainder of our C and SE IL obs at or below
freezing. Will need to include a mention of freezing rain a bit
farther south this morning as a result. Road surface temps on IDOT
sites showing road temps ranging from 34 to as low as 31F. We could
see some slippery road conditions develop with this initial rain
falling on dry pavement. Air temperatures should rise above freezing
across the board by 15z/10am, so any icing would melt quickly.
However, any ice on initially dry roads can be very slippery.

Will follow the HRRR depiction of rain advancing eastward in a band
that matches the current radar trends rather closely. Likely and
categorical PoPs this morning will be confined to the western
counties where low level saturation will occur the soonest.

The band of warm F-gen will gradually shift north this afternoon,
giving the precip a northward push as well. Have kept likely PoPs
across the northern half of our area through the afternoon.

Instability params support elevated thunderstorms today, generally
in the southwest half of our forecast area.

High temps today will be held in check by the cool east-northeast
flow that will persist through the day. Most areas will see the
mid-upper 40s this afternoon.

&&

.LONG TERM...(Tonight through Monday)
ISSUED AT 329 AM CDT TUE MAR 24 2015

Deepening surface low pressure currently at 1006 mb over the OK
panhandle to eject ne into the IL river valley over central IL by
06Z/1 am tonight and then to southern part of Lake MI by 12Z/7 am
Wed and swing a cold front through central and eastern IL overnight.
Showers likely ahead of this front along with chances of
thunderstorms. SPC has marginal risk over much of central IL
(excluding Knox, Stark and Marshall counties) with slight risk of
severe storms this evening across central and sw MO from St Louis
southwest. Lows tonight range from upper 30s to near 40F over IL
river valley to upper 40s and lower 50s in southeast IL.

Central IL to be inbetween weather systems during the day Wed as low
pressure passes ne of the Great Lakes and another surface low
pressure organizes over the southern plains. Isolated showers and
thunderstorms to be possible later Wed afternoon south of I-72.
Milder highs Wed mostly in the 60s, ranging from around 60F from
Peoria north to upper 60s and lower 70s in southeast IL. 1007 mb low
pressure to track ne into far southern IL by 06Z/1 AM Wed night and
up the Ohio river to near the OH/KY border by dawn Thu. Models have
trended further south with this low pressure track, and SPC has
shifted slight risk of severe storms Wed night south of our CWA with
marginal risk into southeast counties along and south of I-70. Heavy
rains of 1-1.5 inches possible south of I-70 Wed night while rain
chances taper off to 20-30% nw of the IL river. Lows Wed night range
from mid 30s over IL river valley to 40-45F in southeast IL from I-70
southeast.

Lingered a chance of rain showers in southeast IL Thu morning then
low pressure moves into southcentral PA by midday Thu and far enough
way to end rain chances Thu afternoon. Much cooler highs Thu in the
mid to upper 40s central IL and near 50F southeast IL. Even colder
Friday with highs in the upper 30s and lower 40s, coolest from I-74
ne. Models have been consistent in digging strong upper level trof
into the eastern states Thu/Fri bringing in the very cool
temperatures. 1030 mb Canadian high pressure settles into the Great
Lakes region Fri night and Sat with clouds and winds decreasing and
continued cold temps. Lows Fri night in the low to mid 20s. Highs
Sat in the low to mid 40s.

A cutoff upper level low passes north of the Great Lakes Sunday
keeping best chances of precipitation north of central IL, though
did carry small chances of light rain showers Sunday. Milder highs
Sunday and Monday in the mid to upper 50s with west central IL
around 60F.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
ISSUED AT 1105 PM CDT MON MAR 23 2015

Main concern will be with the threat for a brief period of light
freezing rain at SPI and possibly as far east as DEC in the 10z-
14z time frame. Surface temperatures will be right around the
freezing mark through this time frame so some light icing is not
out of the question before temperatures edge into the middle 30s
by mid to late morning. Further north and east, the latest short
term models suggest the precip may struggle to shift north before
15z so will hold back the precip threat up at PIA and BMI until
after 15z. By then, it appears the precip would be mostly rain
with the possibility for some isolated convection over parts of
west central and central IL during the morning. For now, will hold
off mentioning any -tsra during the morning withe better threat
for isolated thunderstorms coming along tomorrow night. MVFR and
local IFR cigs will prevail thru most of this forecast period with
periods of rain into tomorrow evening as a storm system is
expected to track right over our area Tuesday night.

Surface winds will remain out of the northeast to east tonight at
10 to 15 kts and then easterly winds will prevail Tuesday with a
gradual turn into the southeast and then south Tuesday evening as
the surface low approaches our area. Wind speeds tomorrow will
range from 12 to 17 kts with gusts around 22 kts at times,
especially during the afternoon and evening hours.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Shimon
LONG TERM...07
AVIATION...Smith





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